Hydraulic feed system



Dec. `1, 1953 H. ERNST HYDRAULIC FEED SYSTEM 3 Sheets-Sheet l Filed Oct. 6, 1951 INVENTOR.

HNS ERNST.

xoamuxngu 4 ATTORNEYS H. ERNST 2,660,985

HYDRAULIC FEED SYSTEM 3 Sheets-Sheet 2 Fig.4

12/ aww 32 Dec. 1, 1953 Filed 0012. 6, 1951 INVENTOR. HANS [NS Eli Q. 5

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1 TTORNEYS.

Dec. l, 1953 H. ERNST 2,660,985

HYDRAULIC FEED SYSTEM Filed Oct. 6, 1951 I5 Sheets-Sheet 3 l-T' :L g .1U

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` HAINS ERNST.

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Patented Dec. 1, 1953 UNITED STATES TENT OFFICE HYDRAULIC FEED SYSTEM Application October 6, 1951, Serial N o. 250,091

1 claim. l

This invention relates to machine tools and more particularly to a new and improved transmission mechanism therefor.

One of the objects of this invention is to provide-a new and improved variable speed transmission and control mechanism for actuating traveling supports of machine tools, which will maintain the selected variable speed substantially constant regardless of changes in load on the support.

Another object of this invention is to provide an improved hydraulic transmission mechanism for feeding a movable support at predetermined feed rates which is so contrived that the rate will not vary upon changes in load, or will not be aiected by changes in viscosity of the actuating fluid.

Other objects and advantages of the present invention should be readily apparent by reference to the following specication, considered in conjunction with the accompanying drawings'for'ming a part thereof, and it is to be understood that any modications may be made in the exact structural details there shown and described, within the scope of the appended claim, without departing from or exceeding the spirit of the invention.

In the drawings in which like reference numerals indicate like or similar parts:

Figure l is a diagrammatic view showing one embodiment of the invention.

Figure 2 is a diagrammatic view showing a modied form of the invention.

Figure 3 is a rolled out view of the servo-valve.

Figure 4 is a detail section on the line li-4 of Figure 3. p

Figure 5 is a detail section on the line 5-5 of Figure 3.

Figure 6 is a detail section on the line 5 6 of Figure 4. y

Figure '7 is a detail section on the line 'l-l oi' Figure 5. f

Figure 8 is a vertical section through the motor and brake shown in Figure 1. Y

Figure 9 is a vertical section on the line 9--9 of Figure 8.

Figure 10 is a vertical section on the line lil-I0 of Figure 8. l y

It is well known in the use of hydraulic transmissions for feeding supports or loaded members mitted to the moving support.

of machine tools and the like that variations in load react on the power unit of the transmission to cause variations in the feeding rate, and that changes in the viscosity of the actuating Viluid have a similar eect. In the field of precision machines, such as machine tools, for instance, it is highly desirable to be able to move the actuated member at some constant rate unaffected by change in load, and to maintain the same rate throughout a days operation without effects from changes in viscosity of the operating fluid caused by changes in the temperature thereof.

In carrying out this invention, there has been provided first a monitoringV driving mechanism with adequate control to positively maintain a desired speed of operation, and which is not connected to be responsive tol any effects from changes in load on the actuated member. In othenwords, this mechanism drives against'a substantially constant load. Secondly, this monitoring mechanism is coupled to the main actuating motor by means of a servo-control mechanism which positively ycauses the main motor to rotate at the same or proportionate speed as the monitoring mechanism and thus by maintaining the revolutions per minute of the main motor equal or proportionate tothe revolutions per minute of the monitoring motor the eiects of viscosity in the actuating fluid for the main motor is eliminated. The main motor is connected to the actuated member by a positive mechanical transmission, such as a screw and nut as a good illustration, so that the revolutions per minute of the main motor are positively trans- Although the monitoring mechanism operates against a substantially constant load it is still necessary to correct for viscosity where such mechanism is hydraulically operated, and this is accomplished by providing a rate control valve which automatically and independently adjusts for changes in viscosity with the result that these various elements are combined in a new combination to overcome the objections and inadequacies of prior hydraulic transmissions.

For a clearer understanding of the invention, reference will now be had to Figure l in which the reference numeral l0 indicates a sliding support or loaded member of a machine to be actuated or moved at a selected constant rate, relative rotatableplunger Si which is connected to a trip lever 62 having a lug 63 for engagement by trip control dogs Gd and E5 carried by the movable support It. When the reversing valve is in the positionfshown in'Figure l, the pressure port 58 is connected to line t5 and port 61 of valve 53. The reversing valve has a second line 68 leading therefrom to port 69 of valve 53 which, when it is in the position shown, causes its annular groove lo 'to short circuit or interconnect the ports G7 and 69.

Since the port 6'! is a pressure port in the position shown, the iiuid returns through line 68 to exhaust port 'Ii of the reversing valve 59, line 72, rate valve 73, line 14, and low pressure relief valve 'I5 to the reservoir 55. By shifting the valve plunger iii to the right ,by means of the manually operable control lever TI, the annular groove 'le in the valve plunger connects port 61 to port 78, and line 4S to motor 25, while the return line E@ from the motor is connected by the annular groove 'i9 to port 59, thereby causing rotation of the motor in one direction. By rotating the reversing valve 6I the pressure and exhaust connections to the motor 25 may be reversed. It will be noted that in either case the returning iuid from the motor 25 passes through the rate valve '13. This valve may be a known type which automatically maintains the rate of now regardless of changes in viscosity.

Since the load on the motor 25 is substantially constant, and since the rate valve automatically compensates for changes in viscosity in the nuid driving the motor, it will be obvious that a very accurate control of the rate of rotation of the servo-valve may be obtained.

When the slide is stopped and the hydraulic control system is under pressure, any small leakage in the system which would upset the hydraulic balance might cause a creepage of the movable slide, and to guard against this, braking means have been provided for locking the servovalve motor whenever it is stopped. This braking means may be of the conventional spring pressed type of pivoted braking shoe III shown in Figure 9 which is normally urged by the spring II2 into holding position, and therefore whenever the motor is operated the brake must be released. The braking means is enclosed in the housing @d which contains a fluid operab-le piston I I3 slidable in cylinder lili for releasing the brake, and this piston has an annular groove H5 and interdrilled passage IIE communicating with the closed end of the cylinder, and a groove I I4 communicates with port iI'I connected by a h5- drauiic channel 3i to ports 82 and 83 of valve 53. The pressure line 5l has a branch connection to port ed which is normally closed by the valve spool 85 on valve plunger 'I6 when it is in a stop position. Therefore, when the valve plunger i6 is moved either to the left or to the right the pressure port 84 is connected to either port 82 or port 83 whereby the brake is automatically released when the plunger 'I6 is moved to an operative position. The valve 53 also has a pair of exhaust ports 85 and 81 for draining the ports S2 and 83 into return line 88 when the valve is in a stop position, thereby permitting automatic operation of the brake.

When it is desired to manually adjust the support, the valve I5 is shifted to the left by the lever 'I'I into the hand position and is held in that position by the spring pressed detent 89 which cooperates with the dierent grooves 90, 9| and 92 for holding the valve in any one of its three positions. In the 'hand position the pressure line 51 is connected through the ports et and 83 to release the brake 'whereby the motor 25 may be rotated by hand because the motor lines 5i) and 5I are interconnected or short circuited through the annular groove 'i9 in the valve plunger 16.

It will now be apparent that the slide Ill may be manually adjusted through manual rotation of the hand wheel 93 of the motor 25 when the valve plunger I1 is shifted to the left; or it may be power operated by shifting the plunger il to the extreme right in which case a reciprocating cycle may be obtained by properly adjusting the trip dogs Ylill and E5 on the slide for engagement with the trip vlever `ft2 of the reversing valve Se.

In Figure 2 a modiiication of the invention .is shown in which the servo-valve is driven by an electric motor 94 instead of a hydraulic motor, and this motor is connected in the same way through gears 24 and 23 to the servo-valve indicated generally by the reference numeral I9. The motor has two leads 95 and 9&3 which are connected through a reversing switch indicated diagrammatically by the reference numeral 9'! to a pair of leads 98 and 89. The lead 98 is connected to a rheostat Illilfor controlling the speed of the motor, one end of the rheostat being connected by line IBI to a power main H12. The other power main |03 is connected by a line Idd to a control switch I 05 which in the position shown in Figure 2 connects power to both line 99 and to a second line I0@ which leads to the brake housing |01 for electrically removing the brake contained in said housing which is normally in a clamping position when the brake is deenergized. The reversing switch it? may be connected to the trip lever 552 for dog operation by the trip dogs 64 and 65 in the same manner as previously described.

By moving the switch lever H35 to its stop position indicated by the reference numeral ISS, all power is disconnected from the motor 9d and the brake I l, whereby the servo-valve Ie is held in a stop position. By shifting the switch lever |35 to the position indicated by the reference numeral IUS power is connected simply to the line I-6 to release the brake so that the motor S4 may be rotated by the hand wheel I I for manual adjustment of the slide. Thus, the servovalve may be rotated in the same manner as before for controlling the movement of the slide IU.

There has thus been provided a new and improved transmission mechanism for actuation of machine slides, such as the feeding of machine tool slides which are subjected to variable loads as the work piece attached to the slide engages the cutter and as the cutting operation progresses, which will maintain a steady and uniform rate of slide movement regardless of variations in the cutting load, and in which the rate will not be affected by variations in the viscosity of the actuating hydraulic uid, and which is so contrived that these variable factors are isolated from the monitoring mechanism which sets up and maintains the feeding rate so as to be unaiectable thereon.

What is claimed is:

In a transmission and control mechanism for feeding a machine slide relative to its support,

' the combination of interengaging motion transment of the slide, a source or iuid pressure for said motor, a rotary servo-valve having a stop position for connecting said source of pressure to motor including relatively movable Valve one of which is movable in response to ac tuation of said motor, a second hydraulic motor for driving said other valve part, said second motor having a pair of channels connected thereto through which fluid is circulated to di'ive said motor, a uid operable brake for said second motor, manually operable for rotating; said seeonc motor, and a seieczor valve having a first position for ieleasing said brake, and connectingiuid pressure to said channels to effect operation of the sec-ond motor, a seeond position for disconnecting fluid pressure from said channels and causing application o1 said brake, a' third position for interconnecting said channels and releasing said brake for manual operation of the second motor.

HANS ERNST.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,231,137 Dickert June 26, i917 2,058,642 Sperry Oct. 27, 1936 2,138,050 Vickers Nov. 29, 1938 2,324,750 Wiedmann July 20, 1943 2,349,641 Tucker May 1944 2,373,226 Coates Apr. 10, 1945 2,395,979 Tucker et a1 Mar. 5, 1946 2,403,924 Herman et al July 15, 1946 2,406,482 Tucker Aug. 27, 1946 Shader Feb. 24, 1948 

